How do you concatenate the rows of a matrix into a vector in MATLAB?

Question

For an m-by-m (square) array, how do you concatenate all the rows into a column vector with size m^2 ?

Answer 1

There are a couple of different ways you can collapse your matrix into a vector, depending upon how you want the contents of your matrix to fill that vector. Here are two examples, one using the function RESHAPE and one using the colon syntax (:):

>> M = [1 2 3; 4 5 6; 7 8 9];  %# Sample matrix
>> vector = reshape(M.',[],1)  %'# Collect the row contents into a column vector

vector =

     1
     2
     3
     4
     5
     6
     7
     8
     9

>> vector = M(:)  %# Collect the column contents into a column vector

vector =

     1
     4
     7
     2
     5
     8
     3
     6
     9